A magnetic disk drive is described hereinafter as an example of conventional disk drives. Recently the market of mobile information apparatuses such as PDAs (personal digital assistants), personal computers has been expanded, and those apparatuses have been downsized, so that magnetic disc drives, one of major data storage devices, are required to be highly portable, e.g. to be downsized and slimmed, and to have shock robustness. To meet these requirements, a magnetic disk drive employing disk-shaped magnetic recording media measuring as small as 0.85 inch (approx. 22 mm) across has been recently developed. (e.g. refer to “Development of 0.85 inch hard-disk drive mountable to mobile apparatus” by TOSHIBA Co., Ltd. Jan. 8, 2004, access to URL: http://www.toshiba.co.jp/about/press/2004—01/pr_j0801.htm. or access to URL: http://www.toshiba.co.jp/about/press/2004—03/pr1601.htm.)
The head supporting unit of such magnetic disk drives for mobile application has been generally held by a load/unload method (hereinafter referred to simply as L/UL method).
FIG. 11 shows a perspective view schematically illustrating the structure of magnetic disk drive 100 that employs a conventional L/UL method. When disk drive 100 shown in FIG. 11 is at rest, head supporting unit 108 rotates on bearing 105, so that slider 101 placed at the tip of unit 108 moves to the outer side of magnetic recording medium 107. Magnetic head holder 110 is provided to the outer side of medium 107, and slider 101 supported by suspension 102 runs up to be held onto the ramp of holder 110. This mechanism allows preventing slider 101 from colliding with magnetic recording medium 107 even if an impact applied to the disk drive 100.
When the disk drive starts operating, i.e. when magnetic recording medium 107 starts spinning, head supporting unit 108 rotates on bearing 105 in reversal direction to the foregoing case, so that slider 101 is loaded onto medium 107. At this time, slider 101 possibly touches medium 107, so that disk drive 100 employing the L/UL method needs evacuation area “O” at the outer rim of medium 107 for parking slider 101. This evacuation area “O” cannot be recorded magnetic data, so that the presence of evacuation area “O”, which must be prepared at the outer rim, becomes a hurdle to the request of increasing the storage capacity as much as possible.
On the other hand, the CSS system needs no such an evacuation area at an outer rim of a recording medium. FIG. 12 shows a structure of magnetic disk drive 120 employing a conventional CSS system. Magnetic recording medium 107 under the CSS system has area “A” where magnetic data can be recorded and area “B” is an evacuation area (hereinafter referred to as a CSS area) where slider 101 having a magnetic head is parked when disk drive 120 is at rest. When medium 107 stops spinning, slider 101 touches medium 107 at CSS area “B”; however, when data is recorded or reproduced, namely, spindle motor 109 starts rotating, the magnetic head provided to slider 101 flies from medium 107, and records or reproduces data in area “A”. When medium 107 in disk drive 120 stops spinning, head supporting unit 108 firstly rotates with slider 101 flying, then slider 101 moves into CSS area “B”. Then as the rpm of medium 107 lowers, the airflow between medium 107 and slider 101 decreases, so that the flying force for slider 101 is lowered, and consequently the magnetic head or slider 101 touches medium 107 and comes to rest.
CSS system magnetic disk drive 120 needs an evacuation area as well, i.e. the foregoing CSS area “B” where the magnetic head or slider 101 is parked and no data is recorded as evacuation area “O” of the L/UL method cannot be recorded data. However, the CSS system is to form CSS area “B” at an inner circumferential side of medium 107, so that the ratio of CSS area “B” vs. total area of medium 107 can be smaller than the ratio of evacuation area “O” of L/UL method vs. total area of medium 107. In other words, when both of the CSS system and L/UL method use magnetic recording media 107 having the same storage capacity, the CSS system can use a greater storage area than the L/UL method.
In the foregoing conventional CSS system magnetic disk drive, the slider or the magnetic head touches the magnetic recording medium when the disk drive is at rest. Thus whenever the disk drive starts or stops operating, the spindle motor rotates with the slider or the magnetic head rubbing against the recording medium. This mechanism possibly incurs magnetic or mechanical damages to the slider, magnetic head, and magnetic recording medium. Thus the CSS system magnetic disk drive has been said that it is inferior to the L/UL system disk drive in durability, and is not fit for a mobile application.